Amplification system



June 5, 1928. 1,672,010

A. H. TAYLOR AMPLIFIVCATION SYSTEM Filed Aug. 19, 1927 2 Sheets-Sheet' 1 ATTORNEY June 5, 1928.

A. H. TAYLOR AMPLIFICATION SYSTEM Filed Aug. 19, 1927 2 Sheets-Sheet 2 ThE NVENTOR., maar 3l@ 55W A TTORNEY wherein Patented June 5, 1928.

' UNITED STATES.

PATENTv orrlci'a.l

.ALBERT H. TAYLOR, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TO WIRED t RADIO, INC., OF vNEW YORK, N. Y., A CORPORATION OF, DELAWARE.

AMPLIFICATIQN SYSTEM.

Application lediAugust 19, 1922. Serial MNro. 214,073.

My invention relates broadly to high power electron tube transmitter circuits and more particularly to a system of power transfer for transmitter circuits.

@ne of the objects of my invention is to provide a circuit arrangement for a high frequency oscillator and power amplifier in a signal transmitter system for stabilizing the operation of the tube circuits and elfecting a transfer of high frequency energy at high power.

Another object of my invention is to-provide a circuit arrangement for a piezo electric crystalcontrolled transmitter wherein a system of series plate tuning is provided in the power amplilier system for balancing the operation of the circuit and preventing violent self-oscillations which are liable to lriclr back into the crystal circuit and imair the operation of the crystal.

Still another object of invention resides in thearrangement of series plate tuning for the electron tube circuits of a, high power transmitter, as described more fully in the specification hereinafter following by reference to the accompanying drawings Y l shows a piezo electric crystal controlled oscillator and power amplifier circuit showing one system for balancing the operation of the circuits; Figs. 2 and 3 illustrate diagrammatically the electrical elements in the `circuit of Fig. l; Fig.. e illustrates the series plate tuning arrangement of rny invention in an electron tube transmitter Figure system; and Figs. 5 and 6 diagrammatically illustrate the elements included' in thelcircuit of ll`ig. d.

Figure l shows a master oscillator power ampiiiier circuit with a balance between the power amplifier l and the master oscillator 2. The particular circuit illustrated uses a parallel high voltage feed to` plate and piezo electric control. Various methods of -keying the circuit may be provided.

The master oscillator includes the piezo electric crystal lelement 1l) connected in the input circuitof the master oscillator 2, with suitable radio frequency choke 11 arranged with respect thereto for securing operation of the oscillator with substantially no load upon the piezo electric crystal element il). l'iie output circuit of the oscillator 2 includes power amplilier the inductancc system 12 having-a portion thereof tuned by means of condenser 14.-. A blocking condenser 15 is arranged in circuit with inductance 12, permitting the passage of .high frequency oscillations through the inductance 12, while preventing the passage of direct current from the excitation source of the plate circuit. The radio frequency choke coil 16 prevents high frequency currents from reaching the source of direct current potential. The cathode of the oscillator 2 is heatedfrom a suitable source represented at 17. By adjusting the tap 18 'on 1nductance'12 and controlling the position of condenser 14, the circuits can be adjusted to the desired condition for 'sustaining oscillations having the frequency of piezo electric crystal element il). 'l he power amplifier system l has its input circuit connected with 'the output circuit of the master oscillator by means of a tan 20 on inductance l2 and al connection 21 along the inductance l2. The power amplifier tube l and its grid electrode are biased from source 22 through radio frequency choke coil 23. A blocking condenser 25 is connected with the grid circuit of 'the power amplifier l. Theportion of inductancel2 i dr'cated at 26 operates in conjunction with the adjustable connector 27 connected at point 28 in amplier l balancing the operation of The high potential i for the power amplifier.

the output circuit of power source for exciting the power ampliier l is obtained through choke coil 29; 'lhcplate circuit or inductance 3 may have a portion thereof shunted ,by condenser l. Condenser 30 is placed in -`series in the output circuit with the inductance 3. l have illustrated connections. from the inductance 3 to a succeeding stage of amplification or to a load circuit, such as an antenna and ground or counter-poise system.

Fig. 2 shows a schematic diagram of the circuit without 'the balance and without any load such as'an antenna, or second ampliher on the plate circuit. lt will be seen that this circuit shown in Fig. 2 is not one with a single resonance point but is complicated by the fact that there is acapacity in parallel with a portion of the plate circuit inductance. For the case of low frequencies where the inductance becomes ultimately large and the parallel plate tuningr negligible as far as its influence on the circuit is concerned. In considering small variations, however, this approximation naturally cannot be made. iVhen the circuit is considered with the addition of thc balance 26-27 and by an antenna load having constants L, R, C, as-shown. in the schematic diagram, Fig. 3, it is not unnecessarily comy plicated` at low frequencies, particularly if nov u CD i the balance condenser 27 is relatively small v and the coupling to the antenna system is' relatively loose. But, as pointed out, Fig. 2

becomesa complicated circuit as soon as high frequencies are approached where the inductances become very small and the high capacity Cp carries a .relatively large value of radio frequency' current. In' such cases this plate capacity has a very marked influence on the tuning-and the circuit is'complicated by having morethan one' tuning point. This complication is, of course, parf` ticularly aggravated when the balance arrangement is put in and the antenna coupled to the transmitter. It is tobe understood that in the place of the antenna a second amplifier tube can be coupled in, either with or without balance. The driving E. M.

F. in the schematic diagram of Figs. 2 and 3 must be considered as being applied between the point A and D.'

' Fig. 4c shows the application of my improved modified series tuning system to a transmission circuit wherein the`p'aralleling of a portion of the plate circuit inductance 3 by a tuned condenser 4 (Fig. 1) is avoided,v

but where the plate filament capacity Cp is augniented by a preferably adjustable condenser placed immediately inf parallel with itinside the condenser 6. The advantage of this circuit arrangement, which I have i termed the modifiedA series plate tuning, consists in the addition of this condenser 6, thus permitting an adjustment of external and internal impedance when it comes to transferring the plate circuit energy to an antenna, another amplifier, or any form of load.

Fig. 5 shows the schematic diagram of a plate circuit thus tuned, but without antenna or other load, and Without balance. The plate circuit capacity Cp -is augmented and can be represented by a single capacity'between points Aand D, at which the driving E. M. F. is applied The blocking condenser load circuit as shown in Fig. 6, itS now has y more than one degree of freedom, but 1f the balance condenser is kept fairly small and the coupllng series. loose, it does approximate the very simple condition shown in Fig. 5` and in any case, it is a vastly simpler circuit theoretically than the circuit shown4 in Fig. 3. Only now, it is vfound that especially at the higher frequencies, lsay (3000 kcs. and upwards, the circuits repree' sented by Figs. 1L23 are extremely difiicult to handle without getting into various 'troubles due to erratic tuning, self-oscillations of amplifiers, excessive plate currents,

impurity of wave form and other diiiiculties'. On the other hand, circuits shown in Figs. 4 5-6 with the modified plate tuning are applicable for a wide range of tube types and have demonstrated .themselves to be of remarkably good efficiency and free from practically all of the difficulties previously mentioned. This particular circuit has been tried with 50-watt thoriated iilament tubes, 250-watt thoriated filament tubes, and l k. w. thoriated filament tube and with a special tube for higher frequencies which is not a standard tube. They have alsov been tried with a water cooled tube with excellent results from the point of view of output, ease of' carrying out the balance and stability.

' Itmust be specifically noted-that/fthe one kilowatt air cooled tube, known as General Electric type 851, and known in the Naval VService as CG 2172, has heretofore given an immense amount of trouble in all radio operations. The United States Naval Research Laboratory at Bellevue, lAnacostia, D. C., has, overa period of two and one'- half years, been endeavoring to get this type o'f tube to work properly as a power ampli-v fier at frequencies higher than 3000 kcs. with practically no success at all higher than 4000 kcs. and with very unstable adjustment. This particular tube is a low voltage tube; normal operating voltage being 2000V volts on the plate. This means, therefore, that it has to carry a high plate current in the neighborhood of one ampere and that the internal inter-electrode capacities are very large. This tremendously aggravates the bad condition explained when circuits similar to circuits shown in Figs. 1-23 are used, but, onl the other hand, with the circuits shown in Figs. 4-5-6 this tube, which for more than two years has defied all efforts to produce satisfactory power amplifier action at high frequencies, operates in a highly satisfactory manner. The positioning of the condenser 6 in the circuit permits a considerable variation in the plate circuit tuning inductance and gives the circuit the proper ratio to make its operation efficient -fo'und to be very practical in high power transmitter operation, and While l have described a preferred arrangement of circuit,

l desire that it be understood that modifications may be made and that no limita# tions upon my invention are intended other than are imposed by the scope of the appended claims. fX

lWhat l claini as new and desire to secure by Letters Patent of the United States is as follows: n

1. lin an electron tube transmission system a piezo electric crystal controlled oscillator circuit, a power amplifier connected with said oscillator circuit, said power amplifier including input and output circuits, a circuit including inductance, a condenser in series therewith, a condenser in parallel with said inductance and said aforementioned condenser, connections between said output circuit and said last mentioned condenseixfor the transfer of power to said inductance while preventing the kick-back of energy into said piezo electric crystal controlled oscillator circuit.

2. An electron tube transmitter. circuit `comprising a piezo electric crystal controlled oscillator, a power amplifier having an input circuit and an output circuit, connections between said input circuit and said piezo electric crystal controlled oscillator, a circuit f including an inductance, a condenser in series with said inductance, and a condenser connected between one side of said afore' mentioned condenser and a point in said inductance, said last mentioned condenser bemg disposed in parallel with the output circuit of' said power amplifier for the transfer of high frequency energy from said power amplifier to said inductance while preventing the. kick-back of energy upon .said piezo electric crystal controlled oscillator.

3. An electron tube transmission system comprising a piezo electric crystal controlled oscillator, a power amplifier stage constituted by an electron tube having grid, filament and plate electrodes, an input circuit extending between said grid and filament electrodes and coupled with the output circuit of said piezo electric crystal controlled oscillator, an output circuit extending between the plate and filament electrodes of said power amplifier stage, said output cir'- cuit including a connection to-an inductance from the plate electrode through a condenser, and a connection from a point in said inductance to said filament electrode, and a condenser connected in shunt with said plate and filament electrodes and across a series circuit constituted by said first mentioned condenser and induct'ance for facilitating the transfer of power from said power amplifier stage while preventing the kick-back of energy .upon said piezo electric crystal controlled oscillator.

4. An electron tube transmitter system comprising a piezo electric crystal controlled oscillator, a power amplifier constituted by an electron tube having grid, filament and plate electrodes, an input circuit connected between said grid and filament electrodes and coupled with said piezo electric' crystal controlled oscillator, an output circuit extending between said plate and filament electrodes, said output circuit being shunted by means of a condenser, and connections eX- the kickx-back of energy upon said piezo electric crystal controlled oscillator. ALBERT H. TAYLOR, 

